Enforce issue dependencies: a derived blocked label, an assignment guard and a required pull-request check #1034

Summary

Work that depends on other work is recorded only in prose today ("after S8", "Settle #706 first", "don't start without coordinating on #894"). Nothing stops a contributor from claiming or opening a pull request for an issue whose prerequisite is still open, and nothing tells them when it opens up. This issue turns dependencies into an enforced contract.

What exists today

• GitHub's native Blocked by links mark an issue as blocked in the sidebar, the Issues list and the project board, but they cannot be filtered (is:blocked returns nothing), they do not reach the project views or the good first issue page, and no workflow event fires when a link is added or removed.
• tools/assign_on_comment.py refuses deferred, security, needs-triage, epic and phase: 16 issues, but knows nothing about dependencies.
• No pull-request check looks at the issues a pull request links.

Design

1. Source of truth: native Blocked by links, set by a maintainer in the issue's sidebar. A dependency written only in prose does not count.
2. A blocker is resolved only when it is closed as completed. A blocker closed as not planned or as a duplicate did not deliver what the dependent waits for, so the dependent stays blocked, gets needs-triage and one comment asking a maintainer to re-plan it.
3. blocked is a derived label, never set by hand: a sync job adds it to every open issue with an unresolved blocker and removes it everywhere else. It runs when an issue is closed or reopened, hourly as a backstop for link edits, and on demand. When it removes the label from an issue that was waiting, it posts one comment; no comment when an issue becomes blocked.
4. Contributor gates: /assign refuses a blocked issue and says why; a pull-request check, Issue dependencies, fails while an issue the pull request links (Fixes / Closes / Resolves / Refs #N) is blocked, unless the same pull request closes every open blocker (in the form GitHub closes on merge) or a maintainer labels it dependency-override (the label set by anyone else is ignored). The check runs on pull_request_target, so both the workflow and the script come from the default branch and no pull-request code is checked out. Every sync run also re-runs the check of each open pull request whose last result no longer matches its linked issues.
5. Views: the project gets a Blocked view; Front door and Small tasks hide blocked issues.

Dependencies recorded with this change

From a review of all open issues (bodies and comments; the prose matches that describe code behaviour, such as "the digest depends on whether xxhash is installed", are not dependencies):

• Phase 16 runs in step order ("each with verified findings fixed and committed before the next step begins"): S5 ← S4, …, S16 ← S15, plus S12 ← [Phase 16] Write the SBOM / supply-chain standard (prerequisite of S12) #889 and S13 ← [Phase 16] Write the Docker standard (prerequisite of S13) #888.
• Deferred items whose recorded condition is another issue: Split forgelm/trainer.py into a sub-package (_kwargs, _runtime, _finalize, _artifacts) — deferred until Phase 16 S4 and S8 have landed #904, Split forgelm/compliance.py into a sub-package (_audit_log, _annex_iv, _provenance, _gdpr) — deferred until Phase 16 S9 has landed #906, Split forgelm/cli/_parser.py into a sub-package (_train, _inspect, _data, _run) — deferred until Phase 16 S5, S7 and S11 have landed #907, Split forgelm/cli/subcommands/_purge.py into a sub-package (_row_id, _run_id, _check_policy, _shared) — deferred until Phase 16 S9 has landed #908, Make the anonymous-operator audit gate config-driven: add compliance.allow_anonymous_operator beside FORGELM_ALLOW_ANONYMOUS_OPERATOR #913, verify-gguf: fail closed by default when no strong layer ran (magic-only verdict) — deferred until the next MAJOR release #915, Publish an official ForgeLM container image — deferred until a weight-redistribution position and the Docker standard exist #916.
• The 72 review issues whose every finding is a unit of one Phase 16 step are blocked by that step; the step's pull request is expected to close them. Grouped issues where only some findings belong to a step are not blocked as a whole: each such finding already carries a KNOWN-OPEN … (Sx open) marker, and CONTRIBUTING asks contributors not to take those finding IDs.

Acceptance criteria

• tools/issue_dependencies.py (sync, check-pr) and its tests; the decision rules are pure functions, the GitHub calls are injected and limited to fixed endpoints.
• .github/workflows/issue-dependencies.yml and .github/workflows/pr-dependencies.yml, least privilege, pinned actions, no ${{ }} in a run: line; tests pin these properties.
• /assign refuses a blocked issue (label or an open native blocker), with a test.
• CONTRIBUTING (labels table, Working on an issue, required checks), CLAUDE.md / AGENTS.md and the CHANGELOG describe the rule.
• Labels blocked and dependency-override exist; the dependencies above are recorded as native links and the labels match them.
• After merge, before 2026-11-02: a repository Actions policy allows pull_request_target for .github/workflows/pr-dependencies.yml only (POST /repos/HodeTech/ForgeLM/actions/policies); GitHub blocks that event in public repositories by default from that date, and the check would stop reporting.
• After merge: the Issue dependencies check is seen attached to a pull request's head commit (it runs on pull_request_target), then added to the required checks of development, and CONTRIBUTING's "not yet among the required checks" sentence is removed.